Amino Acids

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Transcript of Amino Acids

Amino Acids Amelia Fryer Why do we need amino acids? What do they do? Amino acids are the polymers of proteins. There are 20 naturally occurring amino acids used in the human body. All 20 amino acids cannot be made, so some amino acids are obtained through the consumption of plants and meat. Amino acids bond together to form a polypeptide (protein). Proteins are essential to our bodies as they have many different functions. There are structural proteins, like collagen which provide support for tissue in our body e.g. skin. Proteins can also be enzymes, which catalase reactions in our body. There are also contractile proteins like myosin, which helps with the body’s muscle movement. Another type of protein are immunoglobulin proteins. They help our body’s immune system fight against disease. Some proteins are hormones. Hormones regulate the body’s activity e.g. insulin. Proteins can also be receptor proteins which respond to stimuli in our body. There are also transport proteins which carry other molecules e.g. hemoglobin which carries oxygen through the red blood cells. What bonding exists in an amino acid? Let's focus on one amino acid in particular Alanine Intramolecular bonds Covalent bonding occurs within the Alanine amino acid. Covalent bonding is the bonding of 2 nonmetals through the sharing of electrons. On the left of the amino acid, 2 hydrogen atoms are covalently bonded with a nitrogen atom. On the right of the amino acid, there is a double covalent bond between carbon and oxygen. There is also another covalent bond between hydroxide and carbon. Both the NH2 on the left and the COOH on the right have a single covalent bond with the central carbon. CH3 and a Hydrogen atom are also covalently bonded to the central carbon atom. Intermolecular Bonds Alanine bonds with other amino acids to form a protein. This type of bond is called a peptide bond. A peptide bond occurs when the carboxyl group of one amino acid bonds with the amino group of another amino acid and water is released. It is also known as a condensation reaction. Amino group Carboxyl Group What is the overall structure of an amino acid? The general structure of an amino acid consists of 3 parts. The amino group, the carboxyl group and the R group. The R group is the variable group of an amino acid. Each type of amino acid has a different R group. It is the R group of an amino acid that defines which amino acid it is and it’s chemical properties. Amino acids can be categorised into 4 different groups. Non-polar and neutral, polar and neutral, acidic and polar and basic and polar. Non polar amino acids A molecule is considered non polar when the electrons are shared evenly throughout the molecule, creating an even charge throughout the molecule. Non polar amino acids are hydrophobic. This means that they are repelled by water. They also have a neutral pH. This means that they have a pH of seven. Examples of non polar amino acids are Leucine, Methionine and Proline. In humans, we can produce half of the 20 amino acids required in our body. These amino acids are called non-essential amino acids. The other half we must obtain through our diet. These are called essential amino acids. Table of 20 amino acids Many amino acids are produced through transamination. Transamination is the conversion of one amino acid and one keto acid into a different amino acid and keto acid. Keto acids are produced through the second stage in cellular respiration known as the Krebs cycle. So as we ingest certain essential amino acids, they can be converted into other non-essential amino acids in our body. Alanine is one of the non-essential amino acids produced through transamination. It is produced through the conversion of glutamate (essential amino acid) and pyruvate (keto acid) into alanine (non-essential amino acid) and alpha-ketoglutarate (keto acid). Safety concerns of amino acid production It is not the production of amino acids that has risks. It is the breaking down of amino acids. Our body cannot store amino acids, so excess amino acids are broken down and excreted from the body. A product of amino acids being broken down is ammonia, which is highly toxic in our body. To avoid being poisoned, the ammonia in our body undergos chemical reactions to be converted into urea, a less dangerous compound for our body. This is done through 2 processes, firstly deamination and then the urea cycle. Deamination Deamination involves the removal of the amino group from the amino acid through hydrolysis. The amino group has one nitrogen and 2 hydrogen atoms. Another hydrogen is then added onto the compound as a result of hydrolysis. This then turns this compound into an ammonia molecule. + H = (Ammonia) Urea cycle Because the ammonium is toxic, our body has to change it into a less dangerous compound. The body does this through the urea cycle. The urea cycle occurs in the liver. Ammonia (NH3) and carbon dioxide (CO2) are then converted into urea ((NH2)2CO) and water (H20). The urea and water are then transported through the blood from the liver to the kidneys where the blood is filtered, and then it is excreted out of our bodies as urine. As discussed earlier, there are essential and non-essential proteins. There are also conditionally essential amino acids. They are usually non-essential amino acids, however a larger quantity of them are required at certain stages of growth or if someone cannot make them themselves due to a medical condition. This makes them conditionally essential. Phenylketonuria is a genetic disorder that prevents the normal breakdown of the essential amino acid phenylalanine. The amino acid cannot be broken down because the gene in charge of producing the enzyme phenylalanine hydroxylase which breaks down phenylalanine is mutated. Because this amino acid cannot be broken down, the result is the build-up of phenylalanine in the body which can become harmful, causing intellectual disability. An example of when an amino acid becomes conditionally essential The genetic disorder also prevents tyrosine from being synthesized from phenylalanine because phenylalanine cannot be broken down, which is needed for transamination. Therefore, in this case tyrosine becomes a conditionally essential amino acid as more of it has to be consumed to compensate for the lack of it being produced in the body. A molecule is considered polar if the bonded electrons spend more time closer to a particular atom instead of being spread out evenly. Polar amino acids are hydrophilic. This means that they are attracted to water. This is because the negative charge of the oxygen atom in water is attracted to the positive part of the amino acid. The positive charge of the hydrogen atoms in water also attracts the negative part of the amino acid. Some polar amino acids are neutral, some are acidic and some are basic. Acidic amino acids have a pH greater than 7. Basic amino acids have a pH lower than 7. Alanine is a non-polar amino acid. As discussed earlier, non-polar amino acids are also hydrophobic, therefore, Alanine is hydrophobic. Because Alanine is hydrophobic, it will not dissolve in water. R group Polar amino acids Where are amino acids produced? Additional Info •Amino acids: MedlinePlus Medical Encyclopedia. (n.d.). National Library of Medicine - National Institutes of Health. Retrieved April 21, 2013, from http://www.nlm.nih.gov/medlineplus/ency/article/002222.htm•Biochemistry I: Amino Acids . (n.d.). Get Homework Help with CliffsNotes Study Guides . Retrieved April 21, 2013, from http://www.cliffsnotes.com/study_guide/Amino-Acids.topicArticleId-24998,articleId-24958.html•Biochemistry I: Hydrophobic Effect . (n.d.). Get Homework Help with CliffsNotes Study Guides . Retrieved April 21, 2013, from http://www.cliffsnotes.com/study_guide/Hydrophobic-Effect.topicArticleId-24998,articleId-24939.html•Biochemistry II: Amino Acid Biosynthesis . (n.d.). Get Homework Help with CliffsNotes Study Guides . Retrieved April 21, 2013, from http://www.cliffsnotes.com/study_guide/Amino-Acid-Biosynthesis.topicArticleId-24594,articleId-24533.html•Biochemistry II: Urea . (n.d.). Get Homework Help with CliffsNotes Study Guides . Retrieved April 21, 2013, from http://www.cliffsnotes.com/study_guide/Urea.topicArticleId-24594,articleId-24529.htmlhemistry for Biologists: Excretion and the liver. (n.d.). Royal Society of Chemistry | Advancing the Chemical Sciences. Retrieved April 21, 2013, from http://www.rsc.org/Education/Teachers/Resources/cfb/excretion.htm•Deamination. (n.d.). Princeton University - Welcome. Retrieved April 21, 2013, from http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Deamination.html•Mathews/van Holde/Ahern 3rd Edition. (n.d.). Pearson | Higher Education. Retrieved April 21, 2013, from http://www.pearsonhighered.com/mathews/ch20/c20aam.htm•alanine (chemical compound) -- Encyclopedia Britannica. (n.d.).Encyclopedia Britannica. Retrieved April 21, 2013, from http://www.britannica.com/EBchecked/topic/12177/lanine•alanine (chemical compound) -- Encyclopedia Britannica. (n.d.).Encyclopedia Britannica. Retrieved April 21, 2013, from http://www.britannica.com/EBchecked/topic/12177/alanine•protein structure. (n.d.). UCL - London's Global University. Retrieved April 21, 2013, from http://www.ucl.ac.uk/~sjjgsca/ProteinStructure.html•publisher, a. w., & browsed., b. c. (n.d.). Amino Acids Are Made from Intermediates of the Citric Acid Cycle and Other Major Pathways - Biochemistry - NCBI Bookshelf. National Center for Biotechnology Information. Retrieved April 21, 2013, from http://www.ncbi.nlm.nih.gov/books/NBK224 Thank you for watching! References